WHEN the "missing link of electronics" was finally built in 2008, it was the vindication of a 30-year-old prediction. Now it seems the so-called memristor can behave uncannily like the junctions between neurons in the brain.

A memristor is a device that, like a resistor, opposes the passage of current. But memristors also have a memory. The resistance of a memristor at any moment depends on the last voltage it experienced, so its behaviour can be used to recall past voltages.

Now memristors are being used in a US military-funded project trying to make brain-like computers, says Wei Lu, who led the team at the University of Michigan in Ann Arbor that demonstrated the new behaviour (Nano Letters, DOI: 10.1021/nl904092h).

The memristor's existence was predicted in 1971, when Leon Chua of the University of California, Berkeley, spotted a gap in the capabilities of basic electrical components. But it was not until 2008 that Stanley Williams at Hewlett-Packard Labs in Palo Alto, California, made the first memristor from a speck of titanium dioxide, the pigment in most white paint.